सकेसरः स्निग्धो मृदुर्भाजिष्णुश्च निकषरागः श्रेष्ठः ॥ कZ_०२.१३.२० ॥
sakesaraḥ snigdho mṛdur bhājiṣṇuś ca nikaṣarāgaḥ śreṣṭhaḥ
The best touchstone colour/streak is one that is pollen-like (rich), glossy, soft, and lustrous.
They translate metallurgical quality into field-usable criteria for inspectors, enabling standardized grading without advanced instruments.